Method for producing aromatic hydrocarbons

ABSTRACT

A method for producing aromatic hydrocarbons in which at least one feedstock oil selected from the group consisting of LCO produced from an FCC apparatus, hydrotreated LCO, naphtha and straight-run gas oil is brought into contact with a reforming catalyst inside a fluidized bed reactor, wherein the method includes transporting a reforming catalyst that has been extracted from the fluidized bed reactor to a heating tank, heating the reforming catalyst in the heating tank to a temperature at least as high as the reaction temperature inside the fluidized bed reactor, and following heating, transporting the heated reforming catalyst to the fluidized bed reactor.

TECHNICAL FIELD

The present invention relates to a method for producing aromatichydrocarbons. The method relates particularly to a method for producingaromatic hydrocarbons by a catalytic reforming reaction using afluidized bed reactor.

Priority is claimed on Japanese Patent Application No. 2009-078602,filed Mar. 27, 2009, the content of which is incorporated herein byreference.

BACKGROUND ART

Methods for producing aromatic hydrocarbons such as BTX (benzene,toluene, xylene and the like) by catalytic reforming of a light naphthaor heavy naphtha or the like obtained from a fluid catalytic cracking(hereinafter abbreviated as FCC) apparatus are well known. Theseproduction methods generally employ a system based on a fixed bed ormoving bed that uses a granulated reforming catalyst.

Because the reforming reaction is usually an endothermic reaction, themethod used for supplying the heat required by the reaction and thetechnique used for controlling the associated temperature are oftenproblematic issues. Further, the generation of coke that accompanies thereaction operation, which is an issue even when a light naphtha is usedas the feedstock, becomes far more marked when a heavy naphtha orparticularly a light cycle oil (hereinafter abbreviated as LCO) or gasoil is used as the feedstock, and the frequency with which the reformingcatalyst must be regenerated also increases markedly.

In order to address these issues, systems that use a fluidized bedcatalytic reforming method have been proposed instead of theconventional fixed bed and moving bed systems (for example, see PatentDocument 1).

By employing a fluidized bed system, the reforming catalyst of thereaction bed and the feedstock can be maintained in a state that isclose to complete mixing, and therefore maintaining the reactiontemperature at a constant level is simplified. At the same time, in thecase of a heavier feedstock, a reforming catalyst that has been degradedwith coke can be easily extracted from the fluidized bed reactor,enabling catalyst regeneration to be performed smoothly. In other words,when coke adheres to the reforming catalyst due to contact with thefeedstock, the reforming catalyst becomes inactivated, and therefore thereforming catalyst is extracted from the fluidized bed reactor andtransported to a regenerator, and the coke adhered to the reformingcatalyst is combusted inside the regenerator to regenerate the reformingcatalyst. The regenerated reforming catalyst is then transported back tothe fluidized bed reactor.

However, the amount of coke adhered to the reforming catalyst in thefluidized bed reactor is insufficient to allow the combustion of thecoke inside the regenerator to generate the necessary heat for thereforming reaction (endothermic reaction) of the feedstock inside thefluidized bed reactor. As a result, the feedstock must be preheated inheating furnace to a temperature at least as high as the reactiontemperature prior to supply to the fluidized bed reactor.

However, when the feedstock is heated in a heating furnace, some of thefeedstock inside the heating furnace exists at the dew point between amixed gas-liquid state and a completely gaseous phase. Generally, whenfeedstock at the dew point exists inside the heating furnace, impuritiestend to accumulate on the pipes of the heating furnace in the vicinityof the dew point feedstock. These accumulated impurities tend to causelocalized heating, increasing the possibility of damage to the heatingpipes, and therefore preheating the feedstock in this manner is notideal. Further, in those cases where rapid progression of the reformingreaction causes the temperature inside the fluidized bed reactor todecrease abruptly, the required heat cannot be supplied rapidly to thesystem. Accordingly, there are a number of issues that must be addressedin order to enable a fluidized bed reactor to be used for producing aproduct oil containing BTX in an efficient and stable manner.

CITATION LIST Patent Document

Patent Document 1: Published Japanese Translation of PCT No. H 3-503656

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

The present invention provides a method for producing aromatichydrocarbons using LCO produced from an FCC apparatus, naphtha andstraight-run gas oil as the feedstock, which enables the aromatichydrocarbons to be produced in an efficient and stable manner.

Means for Solving the Problem

A method for producing aromatic hydrocarbons according to the presentinvention involves bringing at least one feedstock oil selected from thegroup consisting of LCO produced from an FCC apparatus, hydrotreatedLCO, naphtha and straight-run gas oil into contact with a reformingcatalyst inside a fluidized bed reactor, wherein the method includes:

transporting a reforming catalyst that has been extracted from thefluidized bed reactor to a heating tank,

heating the reforming catalyst in the heating tank to a temperature atleast as high as the reaction temperature inside the fluidized bedreactor, and

following heating, transporting the heated reforming catalyst to thefluidized bed reactor.

The heating of the reforming catalyst in the heating tank is preferablyperformed by combusting, in the presence of an oxygen-containing gas, aheating fuel supplied to the heating tank from an external source.

The heating fuel may be either a liquid fuel or a gaseous fuel, and ispreferably a product oil distillation tower bottom oil obtained from theproduction method of the present invention.

The amount of the heating fuel, for example the distillation towerbottom oil, supplied to the heating tank is preferably within a rangefrom 0.005 to 0.08 tons per 1 ton of feedstock oil supplied to thefluidized bed reactor.

The amount of the reforming catalyst extracted from the fluidized bedreactor is preferably within a range from 5 to 30 tons per 1 ton offeedstock oil supplied to the fluidized bed reactor.

The pressure inside the fluidized bed reactor is preferably within arange from 0.1 to 1.5 MPaG.

The reaction temperature inside the fluidized bed reactor is preferablywithin a range from 350 to 700° C.

The contact time between the feedstock oil and the reforming catalystinside the fluidized bed reactor is preferably within a range from 5 to300 seconds.

Advantageous Effects of the Invention

The method for producing aromatic hydrocarbons according to the presentinvention is a method for producing aromatic hydrocarbons using LCOproduced from an FCC apparatus, naphtha and straight-run gas oil as thefeedstock, which enables the aromatic hydrocarbons to be produced in anefficient and stable manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram illustrating one example of afluid catalytic reforming apparatus used in the method for producingaromatic hydrocarbons according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a schematic structural diagram illustrating one example of afluid catalytic reforming apparatus used in the method for producingaromatic hydrocarbons according to the present invention. A fluidcatalytic reforming apparatus 10 includes a fluidized bed reactor 12, aheating tank 14, a catalyst riser 16, an inclined pipe 18, an inclinedpipe 20, a feed pipe 22, a discharge pipe 24, a fuel pipe 26, anoxygen-containing gas pipe 28, and an exhaust pipe 30. The terminal ofthe catalyst riser 16 is connected to the fluidized bed reactor 12. Thebase of the inclined pipe 18 is connected to the fluidized bed reactor12, and the terminal of the inclined pipe 18 is connected to the heatingtank 14. The base of the inclined pipe 20 is connected to the heatingtank 14, and the terminal of the inclined pipe 20 is connected to thebase of the catalyst riser 16. The base of the discharge pipe 24 isconnected to the fluidized bed reactor 12. The terminal of the fuel pipe26 is connected to the heating tank 14. The terminal of theoxygen-containing gas pipe 28 is connected to the heating tank 14. Thebase of the exhaust pipe 30 is connected to the heating tank 14.

The fluidized bed reactor 12 is used for bringing the feedstock oil intocontact with the fluidized bed of the reforming catalyst to generate aproduct oil containing a large proportion of BTX. The fluidized bedreactor 12 includes a supply port, an extraction port, a cyclone, and adischarge port. The feedstock oil vapor and reforming catalyst that havebeen transported through the catalyst riser 16 are introduced into thefluidized bed reactor 12 via the supply port. The reforming catalyst isextracted into the inclined pipe 18 through the extraction port. Thecyclone is used for separating the vapor of the product oil and thereforming catalyst. The vapor of the product oil that has been separatedin the cyclone is discharged into the discharge pipe 24 through thedischarge port.

The heating tank 14 uses not only the heat generated by combustion ofthe coke adhered to the reforming catalyst, but also energy suppliedfrom an external source to actively heat the reforming catalyst. Inother words, the heating tank 14 is, in itself, a large heating device.The heating tank 14 includes three supply ports, an extraction port andan exhaust port. The reforming catalyst that has been transportedthrough the inclined pipe 18 is introduced into the heating tank 14through the first supply port. The reforming catalyst is extracted intothe inclined pipe 20 through the extraction port. A heating fuel thathas been transported from an external source through the fuel pipe 26 isintroduced into the heating tank 14 through the second supply port. Anoxygen-containing gas that has been supplied through theoxygen-containing gas pipe 28 is introduced into the heating tank 14through the third supply port. Combustion gases generated by thecombustion are discharged into the exhaust pipe 30 through the exhaustport.

The catalyst riser 16 is a pipe-like member that extends in the verticaldirection, and includes a supply port via which the reforming catalystthat has been transported through the inclined pipe 20 is introduced,and a supply port via which a liquid feedstock oil that has beensupplied through the feed pipe 22 is introduced.

Production of aromatic hydrocarbons using the fluid catalytic reformingapparatus 10 illustrated in FIG. 1 is conducted, for example, in themanner described below.

The feedstock oil, which has been preheated using a preliminary heater(not shown in the FIGURE) provided partway along the feed pipe 22, isintroduced continuously from the feed pipe 22 to the catalyst riser 16.At the same time, the reforming catalyst that has been heated in theheating tank 14 is introduced continuously into the catalyst riser 16from the inclined pipe 20, and is transported into the fluidized bedreactor 12 by the vapor of the vaporized feedstock oil rising up thecatalyst riser 16 which acts as a transport medium.

The reforming catalyst that is supplied continuously, together with thevapor of the feedstock oil, from the catalyst riser 16 to the fluidizedbed reactor 12 is converted to a fluidized bed state by the vapor of thefeedstock oil. The feedstock oil vapor and the reforming catalyst makecontact within this fluidized bed state, yielding a product oil vaporthat contains a large amount of BTX. The product oil vapor and thereforming catalyst are separated by the cyclone, and the product oilvapor is discharged continuously into the discharge pipe 24. Thedischarged product oil vapor travels through the discharge pipe 24 andis transported to a distillation tower or the like (not shown in theFIGURE) of a subsequent stage. Coke adheres to the catalyst as a resultof the contact with the feedstock oil vapor, and a portion of thepartially inactivated reforming catalyst is extracted continuously fromthe fluidized bed reactor 12 into the inclined pipe 18.

The reforming catalyst that is introduced continuously into the heatingtank 14 from the inclined pipe 18 is heated continuously to atemperature at least as high as the reaction temperature inside thefluidized bed reactor 12 by combusting the heating fuel, which has beensupplied from an external source through the fuel pipe 26, in thepresence of the oxygen-containing gas that has been supplied through theoxygen-containing gas pipe 28. In other words, the heat of combustiongenerated by combusting the heating fuel and the oxygen-containing gasis used to heat the reforming catalyst. Further, during this heating,the coke adhered to the reforming catalyst also combusts, meaning thereforming catalyst undergoes regeneration during the heating process.The combustion gases generated by the combustion are dischargedcontinuously into the exhaust pipe 30. The heated reforming catalyst isextracted continuously from the heating tank 14 into the inclined pipe20, and is then re-introduced into the catalyst riser 16 from theinclined pipe 20. In this manner, the reforming catalyst is continuouslycirculated between the fluidized bed reactor 12 and the heating tank 14.

As the feedstock oil, at least one oil selected from the groupconsisting of LCO produced from an FCC apparatus, hydrotreated LCO, andnaphtha may be used. In those cases when at least one of these feedstockoils is used, the amount of coke that adheres to the reforming catalystupon contact between the feedstock oil and the reforming catalyst is notnecessarily that large. Accordingly, the production method of thepresent invention is very effective in enabling the efficient and stableproduction of aromatic hydrocarbons from the feedstock oil.

The reforming catalyst contains a crystalline aluminosilicate.

Although there are no particular limitations on the amount of thecrystalline aluminosilicate within the reforming catalyst, the amount ispreferably not less than 10% by mass and not more than 95% by mass, morepreferably not less than 20% by mass and not more than 80% by mass, andstill more preferably not less than 25% by mass and not more than 70% bymass.

Although there are no particular limitations on the crystallinealuminosilicate, examples of preferred aluminosilicates include themedium pore size zeolites such as MFI (Zeolite Socony Mobil-five), MEL(Zeolite Socony Mobil-eleven), TON (Theta-one), MTT (Zeolite SoconyMobil-twenty-three), MRE (Zeolite Socony Mobil-48), FER (Ferrierite),AEL (Aluminophosphate-eleven) and EUO (Edinburgh University-one), and ofthese, MFI and/or MEL-type crystal structures are particularlydesirable. MFI-type and MEL-type aluminosilicates belong to the group ofconventional zeolite structures published by The Structure Commission ofthe International Zeolite Association (Atlas of Zeolite Structure Types,W. M. Meiyer and D. H. Olson (1978), distributed by Polycrystal BookService, Pittsburgh, Pa., USA).

The crystalline aluminosilicate preferably contains gallium and/or zinc.By including gallium and/or zinc, BTX can be produced more efficiently,and the production of non-aromatic hydrocarbon by-products of 3 to 6carbon atoms can be suppressed significantly.

Examples of crystalline aluminosilicates containing gallium and/or zincinclude catalysts in which gallium is incorporated within the latticeframework of the crystalline aluminosilicate (crystallinealuminogallosilicates), catalysts in which zinc is incorporated withinthe lattice framework of the crystalline aluminosilicate (crystallinealuminozincosilicates), catalysts in which gallium is supported on thecrystalline aluminosilicate (gallium-supporting crystallinealuminosilicates), catalysts in which zinc is supported on thecrystalline aluminosilicate (zinc-supporting crystallinealuminosilicates), and catalysts including one or more of these forms.

A gallium-supporting crystalline aluminosilicate and/or zinc-supportingcrystalline aluminosilicate can obtained by supporting gallium and/orzinc on a crystalline aluminosilicate using a conventional method suchas an ion-exchange method or an impregnation method. There are noparticular limitations on the gallium source and zinc source used inthese methods, and examples include gallium salts such as galliumnitrate and gallium chloride, gallium oxide, zinc salts such as zincnitrate and zinc chloride, and zinc oxide.

A crystalline aluminogallosilicate and/or crystallinealuminozincosilicate has a structure in which SiO₄, AlO₄ and GaO₄/ZnO₄structures adopt tetrahedral coordination within the framework. Thesecrystalline aluminogallosilicates and/or crystallinealuminozincosilicates can be obtained by gel crystallization viahydrothermal synthesis, by a method in which gallium and/or zinc isinserted into the lattice framework of a crystalline aluminosilicate, orby a method in which aluminum is inserted into the lattice framework ofa crystalline gallosilicate and/or crystalline zincosilicate.

The heating fuel acts as an additional fuel besides the coke adhered tothe reforming catalyst, and examples include fuels supplied fromexternally (so-called torch oil), such as the distillation tower bottomoil from the product oil obtained in the production method of thepresent invention. In terms of avoiding the problem of degradation ofthe reforming catalyst caused by water vapor, the heating fuel ispreferably a distillation tower bottom oil having a comparatively largeratio of carbon atoms to hydrogen atoms (C/H).

Examples of the oxygen-containing gas include air and pure oxygen,although air is preferred from an economic viewpoint.

The heating of the reforming catalyst is not limited to heatinggenerated by combustion of a heating fuel, and heating may also beperformed using an indirect heating device such as a heater or the like.However, from the viewpoints of heating efficiency and suppression ofreforming catalyst degradation, heating generated by combustion of aheating fuel is preferred.

Because the heat required by the reforming reaction inside the fluidizedbed reactor 12 is supplied by the heated reforming catalyst, the heatingtemperature of the feedstock oil by the preliminary heater (not shown inthe FIGURE) may be any temperature less than the reaction temperatureinside the fluidized bed reactor 12. The heating temperature for thefeedstock oil is preferably not less than 150° C. and not more than 450°C., and is more preferably not less than 180° C. and not more than 350°C.

The pressure inside the fluidized bed reactor 12 varies depending on thetarget reaction yield, but the lower limit for the pressure ispreferably 0.1 MPaG, and more preferably 0.2 MPaG. On the other hand,the upper limit for the pressure is preferably 1.5 MPaG, more preferably1.0 MPaG, and still more preferably 0.5 MPaG. Provided the pressure isat least 0.1 MPaG, BTX can be produced efficiently. Provided thepressure is not more than 1.5 MPaG, the amount of light gas by-productsgenerated by cracking can be suppressed.

The lower limit for the reaction temperature inside the fluidized bedreactor 12 is preferably 350° C., more preferably 450° C., still morepreferably 500° C., and still more preferably 520° C. On the other hand,the upper limit for the reaction temperature is preferably 700° C., andmore preferably 600° C. Provided the reaction temperature is at least350° C., the activity of the reforming catalyst reaches a satisfactorylevel. Provided the reaction temperature is not more than 700° C.,excessive cracking reactions can be avoided.

The lower limit for the contact time between the feedstock oil and thereforming catalyst inside the fluidized bed reactor 12 is preferably 5seconds, more preferably 10 seconds, and still more preferably 15seconds. On the other hand, the upper limit for the contact time ispreferably 300 seconds, more preferably 150 seconds, and still morepreferably 100 seconds. Provided the contact time is at least 5 seconds,the reforming reaction progresses satisfactorily. Provided the contacttime is not more than 300 seconds, the amount of light gas by-productsgenerated by cracking can be suppressed.

The amount of the reforming catalyst extracted from the fluidized bedreactor 12 (the circulation amount) is preferably within a range from 5to 30 tons per 1 ton of the feedstock oil supplied to the fluidized bedreactor 12. This amount is also determined in accordance with theoverall heat balance.

The pressure inside the heating tank 14 is preferably higher than thepressure inside the fluidized bed reactor 12 in order to facilitatetransport of the heated reforming catalyst to the fluidized bed reactor12.

Because the heat required by the reforming reaction inside the fluidizedbed reactor 12 is supplied by the heated reforming catalyst, thetemperature inside the heating tank 14 must be at least as high as thereaction temperature inside the fluidized bed reactor 12. The lowerlimit for the temperature inside the heating tank 14 is preferably 500°C., and more preferably 600° C. On the other hand, the upper limit forthe temperature is preferably 800° C., and more preferably 700° C.

The amount of the heating fuel supplied to the heating tank 14 (in thecase of a distillation column bottom oil), is preferably not less than0.005 tons and not more than 0.08 tons, and more preferably not lessthan 0.02 tons and not more than 0.08 tons, per 1 ton of the feedstockoil supplied to the fluidized bed reactor 12. The amount of the heatingfuel supplied is determined in accordance with the amount of cokegenerated and the overall heat balance.

In the method for producing aromatic hydrocarbons according to thepresent invention described above, the reforming catalyst extracted fromthe fluidized bed reactor is transported to the heating tank and heatedto a temperature at least as high as the reaction temperature inside thefluidized bed reactor, and the heated reforming catalyst is thentransported back into the fluidized bed reactor. Accordingly, by usingnot only the heat from combustion of the coke adhered to the reformingcatalyst, but also the energy supplied from an external source toactively heat the reforming catalyst, the heat required for maintainingthe reforming reaction (endothermic reaction) inside the fluidized bedreactor can be supplied in an efficient and stable manner. As a result,even in those cases where a feedstock oil (such as an LCO) is used forwhich the amount of coke that adheres to the reforming catalyst uponcontact with the reforming catalyst is insufficient, BTX can still beproduced in an efficient and stable manner.

EXAMPLES

An example is presented below.

Example 1

Using the fluid catalytic reforming apparatus 10 having the structureillustrated in FIG. 1, BTX production was performed under the operatingconditions listed below, and the resulting data was used to calculatethe production rate and the like for BTX.

Operating Conditions

Heating temperature of feedstock oil by preliminary heater (not shown inthe FIGURE): 200° C.

Supply rate of the feedstock oil (vapor) to the catalyst riser 16: 1ton/hour

Pressure inside the fluidized bed reactor 12: 0.3 MPaG

Reaction temperature inside the fluidized bed reactor 12: 560° C.

Contact time between the feedstock oil and the reforming catalyst insidethe fluidized bed reactor 12: 18 seconds

Pressure inside the heating tank 14: 0.35 MPaG

Temperature inside the heating tank 14: 650° C.

Supply rate of the heating fuel to the heating tank 14: 0.025 tons/1 tonof the feedstock oil

Supply rate of air to the heating tank 14: 0.80 tons/1 ton of thefeedstock oil

Circulation rate of the reforming catalyst: 17.6 tons/1 ton of thefeedstock oil

An LCO was used as the feedstock oil.

The distillation tower bottom oil from the product oil was used as theheating fuel (torch oil).

A reforming catalyst containing an MFI-type zeolite (particledimensions: approximately 0.3 μm) having gallium incorporated within thelattice framework was used as the reforming catalyst.

During operation, heat was able to be supplied efficiently to thefluidized bed reactor 12 using the reforming catalyst that had beenheated in the heating tank 14, and a product oil was able to be obtainedin a stable manner, without major fluctuations in the temperature insidethe fluidized bed reactor 12.

The amount of BTX contained within the product oil was 43% by mass.

INDUSTRIAL APPLICABILITY

The present invention is useful for producing aromatic hydrocarbonsusing LCO produced from an FCC apparatus, and naphtha as a feedstock.

REFERENCE NUMBER

-   12: Fluidized bed reactor-   14: Heating tank

1. A method for producing aromatic hydrocarbons by bringing at least onefeedstock oil selected from the group consisting of light cycle oilproduced from a fluid catalytic cracking apparatus, hydrotreated lightcycle oil, naphtha and straight-run gas oil into contact with areforming catalyst inside a fluidized bed reactor, wherein the methodcomprises: transporting a reforming catalyst that has been extractedfrom the fluidized bed reactor to a heating tank, heating the reformingcatalyst in the heating tank to a temperature at least as high as areaction temperature inside the fluidized bed reactor, and followingheating, transporting the heated reforming catalyst to the fluidized bedreactor.
 2. The method for producing aromatic hydrocarbons according toclaim 1, wherein the heating of the reforming catalyst in the heatingtank is performed by combusting, in presence of an oxygen-containinggas, a heating fuel supplied to the heating tank from an externalsource.
 3. The method for producing aromatic hydrocarbons according toclaim 2, wherein the heating fuel is a distillation tower bottom oilfrom the product oil.
 4. The method for producing aromatic hydrocarbonsaccording to claim 3, wherein an amount of the distillation tower bottomoil supplied to the heating tank is within a range from 0.005 to 0.08tons per 1 ton of feedstock oil supplied to the fluidized bed reactor.5. The method for producing aromatic hydrocarbons according to claim 1,wherein an amount of the reforming catalyst extracted from the fluidizedbed reactor is within a range from 5 to 30 tons per 1 ton of feedstockoil supplied to the fluidized bed reactor.
 6. The method for producingaromatic hydrocarbons according to claim 1, wherein a pressure insidethe fluidized bed reactor is within a range from 0.1 to 1.5 MPaG.
 7. Themethod for producing aromatic hydrocarbons according to claim 1, whereina reaction temperature inside the fluidized bed reactor is within arange from 350 to 700° C.
 8. The method for producing aromatichydrocarbons according to claim 1, wherein a contact time between thefeedstock oil and the reforming catalyst inside the fluidized bedreactor is within a range from 5 to 300 seconds.